A dynamic message sign is a sign having a message that can be changed by a user. Dynamic message signs can be used to publicly display information that can be changed. For example, dynamic message signs can be used as roadway signs to alert motorists of traffic information or they can be used as commercial signs to advertise business or product information. Dynamic message signs are typically connected to a controller for controlling the message on the sign's display. A controller is typically a computer having a communication interface for communicating with the sign.
Dynamic message signs can also be made up of multiple display units, each of which are responsible for producing part of the sign's display. In a dynamic message sign having multiple display units, the controller must communicate with each display unit in order to refresh the display.
Very often, dynamic message signs fail to communicate properly with the controller. This can be due to a disruption in the communication system or, in the case of a dynamic message sign having multiple display units, it can be due to a damaged display unit. Furthermore, the data sent to the dynamic message sign panel by the controller may become corrupted. Prior art dynamic message signs do not include any ability to detect or correct communication or data errors.